Enabling AlwaysOn Availability Groups is a prerequisite for a server instance to use availability groups. Before you can create and configure any availability group, the AlwaysOn Availability Groups feature must have been enabled on the each instance of SQL Server that will host an availability replica for one or more availability groups.

Important

If you delete and re-create a WSFC cluster, you must disable and re-enable the AlwaysOn Availability Groups feature on each instance of SQL Server that hosted an availability replica on the original WSFC cluster.

Enable AlwaysOn Availability Groups on only one server instance at a time. After enabling AlwaysOn Availability Groups, wait until the SQL Server service has restarted before you proceed to another server instance.

Security

While AlwaysOn Availability Groups is enabled on an instance of SQL Server, the server instance has full control on the WSFC cluster.

Permissions

Requires membership in the Administrator group on the local computer and full control on the WSFC cluster. When enabling AlwaysOn by using PowerShell, open the Command Prompt window using the Run as administrator option.

Using SQL Server Configuration Manager

Connect to the Windows Server Failover Clustering (WSFC) node that hosts the SQL Server instance where you want to enable AlwaysOn Availability Groups.

On the Start menu, point to All Programs, point to
Microsoft SQL Server 2014
, point to Configuration Tools, and click SQL Server Configuration Manager.

In SQL Server Configuration Manager, click SQL Server Services, right-click SQL Server (<instance name>), where <instance name> is the name of a local server instance for which you want to enable AlwaysOn Availability Groups, and click Properties.

Select the AlwaysOn High Availability tab.

Verify that Windows failover cluster name field contains the name of the local failover cluster. If this field is blank, this server instance currently does not support AlwaysOn Availability Groups. Either the local computer is not a cluster node, the WSFC cluster has been shut down, or this edition of SQL Server 2014 that does not support AlwaysOn Availability Groups.

SQL Server Configuration Manager saves your change. Then, you must manually restart the SQL Server service. This enables you to choose a restart time that is best for your business requirements. When the SQL Server service restarts, AlwaysOn will be enabled, and the IsHadrEnabled server property will be set to 1.

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Using SQL Server PowerShell

To enable AlwaysOn

Change directory (cd) to a server instance that you want to enable for AlwaysOn Availability Groups.

Use the Enable-SqlAlwaysOn cmdlet to enable AlwaysOn Availability Groups.

To view the syntax of a cmdlet, use the Get-Help cmdlet in the SQL Server PowerShell environment. For more information, see
Get Help SQL Server PowerShell.

Note

For information about how to control whether the Enable-SqlAlwaysOn cmdlet restarts the SQL Server service, see When Does a Cmdlet Restart the SQL Server Service?, later in this topic.

Using SQL Server Configuration Manager

Connect to the Windows Server Failover Clustering (WSFC) node that hosts the SQL Server instance where you want to disable AlwaysOn Availability Groups.

On the Start menu, point to All Programs, point to
Microsoft SQL Server 2014
, point to Configuration Tools, and click SQL Server Configuration Manager.

In SQL Server Configuration Manager, click SQL Server Services, right-click SQL Server (<instance name>), where <instance name> is the name of a local server instance for which you want to disable AlwaysOn Availability Groups, and click Properties.

SQL Server Configuration Manager saves your change and restarts the SQL Server service. When the SQL Server service restarts, AlwaysOn will be disabled, and the IsHadrEnabled server property will be set to 0, to indicate that AlwaysOn Availability Groups is disabled.

We recommend that you read the information in Follow Up: After Disabling AlwaysOn, later in this topic.

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Using SQL Server PowerShell

To disable AlwaysOn

Change directory (cd) to a currently-enabled server instance that that you want to disenable for AlwaysOn Availability Groups.

Use the Disable-SqlAlwaysOn cmdlet to enable AlwaysOn Availability Groups.

For example, the following command disables AlwaysOn Availability Groups on an instance of SQL Server (Computer\Instance). This command requires restarting the instance, and you will be prompted to confirm this restart.

Disable-SqlAlwaysOn -Path SQLSERVER:\SQL\Computer\Instance

Important

For information about how to control whether the Disable-SqlAlwaysOn cmdlet restarts the SQL Server service, see When Does a Cmdlet Restart the SQL Server Service?, later in this topic.

To view the syntax of a cmdlet, use the Get-Help cmdlet in the SQL Server PowerShell environment. For more information, see
Get Help SQL Server PowerShell.

Follow Up: After Disabling AlwaysOn

After you disable AlwaysOn Availability Groups, the instance of SQL Server must be restarted. SQL Configuration Manager restarts the server instance automatically. However, if you used the Disable-SqlAlwaysOn cmdlet, you will need to restart the server instance manually. For more information, see
sqlservr Application.

On the restarted server instance:

Availability databases do not start up at SQL Server startup, making them inaccessible.

The only supported AlwaysOn Transact-SQL statement is
DROP AVAILABILITY GROUP. CREATE AVAILABILITY GROUP, ALTER AVAILABILITY GROUP, and the SET HADR options of ALTER DATABASE are not supported.

If you permanently disable AlwaysOn Availability Groups on every server instance that hosts an availability replica for one or more availability groups, we recommend that you complete the following steps:

If you did not remove the local availability replicas before disabling AlwaysOn, delete (drop) each availability group for which the server instance is hosting an availability replica. For information about deleting an availability group, see
Remove an Availability Group (SQL Server).

To remove the metadata left behind, delete (drop) each affected availability group on a server instance that is part of the original WSFC cluster.

Any primary databases continue to be accessible to all connections but the data synchronization between the primary and secondary databases stops.

The secondary databases enter the RESTORING state. You can delete them, or you can restore them by using RESTORE WITH RECOVERY. However, restored databases are no longer participating in availability-group data synchronization.

On a server instance that is currently running, using Enable-SqlAlwaysOn or Disable-SqlAlwaysOn to change the current AlwaysOn setting could cause the SQL Server service to restart. The restart behavior on depends on the following conditions:

-NoServiceRestart parameter specified

-Force parameter specified

Is the SQL Server service restarted?

No

No

By default. But the cmdlet prompts you as follows:

To complete this action, we must restart the SQL Server service for server instance '<instance_name>'. Do you want to continue?